JP3594326B2 - Fe-RE-B type magnet powder, sintered magnet, and method for preparing the same - Google Patents

Abstract

The magnetic powder employed for the manufacture of sintered magnets of the RE-T-B class, where RE denotes at least one rare earth, T at least one transition element and B boron, consists of the mixture of 2 powders (A) and (B): a) the powder (A) consisting of grains of RE2T14B tetrahedral structure, T being essentially iron with Co/Fe < 8 % being also capable of containing up to 0.5 % Al, up to 0.05 % Cu and up to 4 % in all of at least one element from the group consisting of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and of the unavoidable impurities, with a Fisher particle size of between 3.5 and 5 mu m; b) the powder (B) being rich in RE and containing Co, having the following composition by weight: RE 52-70 %, including at least 40 % (in absolute value) of one (or more) light rare earth(s) chosen from the group consisting of La, Ce, Pr, Nd, Sm and Eu; Co 20-35 %; Fe 0-20 %; B 0-0.2 %; Al 0.1-4 %; and unavoidable impurities, with a Fisher particle size of between 2.5 and 3.5 mu m. The powder (B) may be obtained by mixing a RE-rich powder (C) containing Co with a B-rich powder (D). <IMAGE>

Description

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【図面の簡単な説明】
【図１】本発明に従う焼結磁石（Ｍ１）の顕微鏡検査用断片を概略的に示す図である。
【図２】合金化技術を使用して取得した同一の組成を有する焼結磁石（Ｓ１）の顕微鏡検査用断片を概略的に示す図である。[0001]
[Industrial applications]
The present invention mainly relates to a magnet powder and a sintered permanent magnet containing a rare earth element RE, at least one transition element T, and boron, wherein the magnet powders have different chemical compositions and measured particle sizes, respectively. The present invention relates to a magnet powder and a sintered permanent magnet obtained by mixing two initial powders, and a method for preparing them.
[0002]
[Prior art and problems]
The following patent publication teaches the use of a mixture of two initial alloys for the manufacture of sintered magnets.
[0003]
JP-A-63-114939 discloses a magnet of the type described above, which is produced from a mixture of two powders, wherein one powder has a RE₂T₁₄A magnet is described that comprises a "matrix" containing either low melting point or high melting point elements, including B type magnet grains and others. This patent publication also states that this second powder needs to be extremely fine (0.02 to 1 μm), which is extremely expensive.
[0004]
JP-A-2-31402 discloses the use of a second powder composed of RE-Fe-B or RE-Fe in an amorphous or microcrystalline state, which is obtained by high-speed solidification requiring special equipment. About.
[0005]
Thus, a simpler and less cumbersome manufacturing method using conventional powder metallurgy to produce sintered magnets with better magnet properties, especially good residual values and high resistance to atmospheric corrosion. It is desired to discover.
[0006]
【means】
In this specification, weight percentages and weights are used unless otherwise indicated.
[0007]
According to the invention, the initial powder is a mixture of two powders having different properties and measured particle sizes and having the characteristics described below.
[0008]
a) The powder (A) has a square structure RE₂T₁₄Consisting of grains with B, T is mainly iron with Co / Fe <8%, also up to 0.5% Al, up to 0.05% Cu, and the total Up to 4% of at least one of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, and W, and unavoidable impurities. Between 5 and 5 μm.
[0009]
The total RE content is between 26.7 and 30%, preferably between 28 and 29%, the Co content is preferably limited to a maximum of 5%, which may be 2% . The aluminum content is preferably between 0.2 and 0.5%, more preferably between 0.25 and 0.35% and the Cu content is preferably between 0.1 and 0.5%. 025 and 0.035%, and most preferably between 0.025 and 0.035%. The B content is between 0.96 and 1.1%, preferably between 1.0-1.06%. The rest is composed of Fe.
[0010]
The powder (A) can be obtained by melting (ingot) or from an alloy produced by co-reduction (coarse powder), and the ingot or coarse powder is converted to H under the conditions described below.₂It is preferred to process under The conditions are as follows: installed under a vacuum or a scavenging chamber, introduced an inert gas at a pressure between 0.1 and 0.12 MPa, and increased the temperature by 10 ° C. to a temperature between 350 and 450 ° C. The temperature is increased at a rate between 500 / h and 500 ° C./h, hydrogen at an absolute partial pressure between 0.01 and 0.12 MPa is introduced, and these conditions are maintained for 1 to 4 hours. After that, it is set under vacuum, an inert gas at a pressure of 0.1 and 0.12 MPa is introduced, and cooled to room temperature at a rate between 5 ° C./h and 100 ° C./h. is there. The inert gas is preferably argon or helium, or a mixture of the two.
[0011]
The powder (A) is then mixed with a gas jet mill, preferably with nitrogen gas, at an absolute pressure between 0.4 and 0.8 MPa of between 3.5 and 5 μm Adjust the powder measurement selection variables to produce a powder with a Fisher measured particle size of.
[0012]
b) Powder (B) is rich in RE, contains Co and has the composition indicated below by weight. Its composition is
52-70% RE, hydrogen content greater than 130 ×% RE, including at least 40% (absolute value) of one or more light rare earth elements selected from La, Ce, Pr, Nd, Sm, and Eu ( Ppm), 25-35% Co, 0-20% Fe, 0-0.2% B, 0.1-4% Al, and unavoidable impurities. It has a Fisher measured particle size between 5 and 3.5 μm.
[0013]
The powder (B) preferably contains substantially no B (the B content is less than 0.05%).
[0014]
This powder (B) is obtained from an alloy which is treated under hydrogen under the conditions described below. The conditions are set under vacuum, introducing an inert gas at a pressure between 0.1 and 0.12 MPa, and up to a temperature between 350 and 450 ° C., 10 ° C./h and 500 ° C. / H, the temperature is increased at a rate of between 0.01 and 0.12 MPa, hydrogen of an absolute partial pressure between 0.01 and 0.12 MPa is introduced, and these conditions are continued for 1 to 4 hours, and then the vacuum is applied. And introducing an inert gas at a pressure of 0.1 and 0.12 MPa, and cooling to room temperature at a rate between 5 ° C./h and 100 ° C./h.
[0015]
Further, it is preferred that the preceding operation be performed prior to treatment with hydrogen under the conditions described below. The condition is to hold the initial alloy at room temperature under hydrogen at an absolute partial pressure between 0.01 and 0.12 MPa for 1 to 3 hours.
[0016]
If necessary, the previous or previously defined final hydrogen treatment can be repeated once or twice. Preferably, the inert gas used is argon or helium, or a mixture of the two.
[0017]
The powder is mainly composed of RE oxides, ie, REH_{2 + e}, Co metal and a small amount of NdCo₂including.
[0018]
The powder (B) is then dried using a gas jet mill, preferably using nitrogen gas, at an absolute pressure of between 0.4 and 0.8 MPa to 2.5 and 3.5 μm. A powder measurement selection variable is prepared and finely ground to produce a powder having a Fisher measured particle size between. The powder (B) preferably has a Fisher measured particle size of at least 20% below that of the powder (A).
[0019]
Since this powder (B) produces the second phase, the total melting temperature (liquidus) of the alloy (B) is desirably below 1080 ° C.
[0020]
c) The powders (A) and (B) are then mixed to produce the final composition, the magnet. In this method, the rare earth element content (RE) is generally between 29.0 and 32.0%, preferably between 29 and 31% and the boron content The amount is between 0.94 and 1.04%, the cobalt content is between 1.0 and 4.3% by weight, and the aluminum content is 0.2 and 0.5%. %, The copper content between 0.02 and 0.05% by weight, the balance being iron and unavoidable impurities. O of the magnetic powder resulting from the mixture (A) + (B)₂The content is generally below 3500 ppm. The weight ratio of the powder (A) in the mixture (A) + (B) is between 88 and 95%, preferably between 90 and 94%.
[0021]
Thereafter, the mixture of powders (A) and (B) is parallel (//) or perpendicular (|) Orienting in a suitable magnetic field and further compressing by a suitable method such as, for example, compression or hydrostatic compression. The compression mold bodies obtained are, for example, 3.5 and 4.5 g / cm³Having a specific mass of between 1050 ° C. and 1110 ° C. and further heat-treated in the usual manner.
[0022]
The obtained densities are 7.45 and 7.65 g / cm³And between.
[0023]
The magnet can then undergo any necessary normal mechanical and surface working operations.
[0024]
The magnet according to the invention belongs to the group RE-TB, wherein RE represents at least one rare earth element, T represents at least one transition element such as Fe and / or Co, and B represents boron. And may contain other minor elements. This is mainly a square phase RE called "T1"₂T₁₄The second phase is mainly composed of rare earth elements and can contain other small amounts of phases. These magnets have the following characteristics.
[0025]
Residual value: Br ≧ 1.25T (// at compression)
Residual value: Br ≧ 1.30T (|In compression)
Intrinsic coercive field HcI ≧ 1050 kA / m (~13 kOe).
[0026]
More particularly, they have a structure consisting of grains of phase T1, which are of substantially uniform size between 2 and 20 μm and make up more than 94% of the structure. They are surrounded by a narrow, continuous margin of the RE-rich second phase, which is a substantially uniform thickness not ≧ 5 μm. This second phase contains more than 10% cobalt.
[0027]
However, although the remanence, residual value and specific energy of the magnet are sufficient, they can be fired by producing powder (B) from a mixture of two powders (C) and (D). Further improvements can be made without affecting the other properties of the magnet, in particular the resistance to oxidation and atmospheric corrosion and the mechanical operation by milling. In addition, judicious choice of powder (D) can significantly reduce the sintering temperature and duration.
[0028]
According to the invention, this additive powder (B) is obtained by mixing two different coarse powdered alloys (C) and (D) and then milling them simultaneously. Coarse powder is powder having particles that pass through a 1 mm sieve.
[0029]
a) Powder (C) is rich in RE, contains Co and has the composition described below by weight. Its composition is
52-70% RE, hydrogen content greater than 130 ×% RE, including at least 40% (absolute value) of one or more light rare earth elements selected from La, Ce, Pr, Nd, Sm, and Eu ( Ppm by weight), 20-35% Co, 0-20% Fe, 0-0.2% B, 0.1-4% Al, and unavoidable impurities.
[0030]
Preferably, it is substantially free of B (B content below 0.05%).
[0031]
The coarse powder (C) is obtained from an alloy that is treated under hydrogen under the conditions described below. The conditions are set under vacuum, introducing an inert gas at a pressure between 0.1 and 0.12 MPa, and up to a temperature between 350 and 450 ° C., 10 ° C./h and 500 ° C. / H, the temperature is increased at a rate of between 0.01 and 0.12 MPa, hydrogen of an absolute partial pressure between 0.01 and 0.12 MPa is introduced, and these conditions are continued for 1 to 4 hours, and then the vacuum is applied. And introducing an inert gas at a pressure of 0.1 and 0.12 MPa, and cooling to room temperature at a rate between 5 ° C./h and 100 ° C./h.
[0032]
Further, it is preferred that the preceding operation be performed prior to treatment with hydrogen under the conditions described below. The condition is to hold the initial alloy at room temperature under hydrogen at an absolute partial pressure between 0.01 and 0.12 MPa for 1 to 3 hours.
[0033]
If necessary, the previous or previously defined final hydrogen treatment can be repeated once or twice. Preferably, the inert gas used is argon or helium, or a mixture of the two.
[0034]
The powder (C) is mainly composed of RE oxide, that is, REH₂₊e, Co metal and a small amount of NdCo₂including.
[0035]
b) powder (D) is boron alloyed with one or more of a series of elements (Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Nb, Mo) And, together with unavoidable impurities, can be obtained from alloys containing between 5 and 70% by weight of boron. It preferably comprises an alloy based on Fe, containing between 5 and 30% by weight of boron, up to 10% of copper, up to 10% by weight of aluminum and up to 8% of silicon. Powder (D) is substantially free of rare earth elements (total content ≦ 0.05%).
[0036]
These alloys are produced using conventional techniques, but they are then subjected to rough wet or dry milling mechanically or using a gas jet mill. Thereafter, the coarse powder (D) is mixed with the hydrogenated coarse powder (C) to form a mixture between 0.05 and 1.5%, preferably between 0.4 and 1.2%. A mixture of final boron content between (B) = (C) + (D) is produced. The homogenized mixture (C) + (D) is then milled to a Fisher measured particle size of 2.5 to 3.5 μm.
[0037]
Powder (B) requires a total fusion temperature (liquidus) below 1050 ° C. to produce the second phase. The powder (B) preferably has a Fisher measured particle size of less than 20% of that of the powder (A).
[0038]
c) Powder (A) has a square structure RE₂T₁₄Containing grains with B, T is predominantly iron with Co / Fe <8%, also up to 0.5% Al, up to 0.05% Cu, and in total Up to 4% of at least one element of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W and unavoidable impurities can be contained, and the measured Fisher particle size is 3.5. And 5 μm.
[0039]
The total RE content is between 26.7 and 30%, preferably between 28 and 29%, the Co content is preferably limited to a maximum of 5%, which may be 2% . The aluminum content is preferably between 0.2 and 0.5%, more preferably between 0.25 and 0.35% and the Cu content is preferably between 0.1 and 0.5%. 02 and 0.05%, most preferably between 0.025 and 0.035%. The B content is between 0.95 and 1.05%, preferably between 0.96-1.0%. The rest is composed of Fe.
[0040]
All compositions are RE₂T₁₄It can be very close to B, with copper and aluminum being absorbed as transition elements.
[0041]
The powder (A) can be obtained by melting (ingot) or from an alloy produced by co-reduction (coarse powder), and the ingot or coarse powder is preferably obtained under the conditions described below. At H₂Process below. The conditions are as follows: installed under vacuum or a scavenging chamber, introduced an inert gas at a pressure between 0.1 and 0.12 MPa, and brought the temperature up to a temperature between 350 and 450 ° C. to 10 ° C. / increasing the temperature at a rate between h and 500 ° C./h, introducing hydrogen at an absolute partial pressure between 0.01 and 0.12 MPa, and continuing these conditions for 1 to 4 hours; After that, it is set under vacuum, an inert gas at a pressure of 0.1 and 0.12 MPa is introduced, and the mixture is cooled to room temperature at a rate between 5 ° C / h and 100 ° C / h. The inert gas is preferably argon or helium, or a mixture of the two.
[0042]
The powder (A) is then mixed with a gas jet mill, preferably with nitrogen gas, at an absolute pressure between 0.4 and 0.8 MPa of between 3.5 and 5 μm A powder measurement selection variable is prepared and finely ground to produce a powder having a Fisher measured particle size of.
[0043]
d) The powders (A) and (B) are then mixed to produce the final composition, the magnet. In this method, the rare earth element content (RE) is generally between 29.0 and 32.0%, preferably between 29 and 31% and the boron content The amount is between 0.93 and 1.04%, the cobalt content is between 1.0 and 4.3% by weight, and the aluminum content is between 0.2 and 0.5%. %, The copper content between 0.02 and 0.05% by weight, the balance being iron and unavoidable impurities. O of the magnetic powder resulting from the mixture (A) + (B)₂The content is generally below 3500 ppm. The weight ratio of the powder (A) in the mixture (A) + (B) is between 88 and 95%, preferably between 90 and 94%.
[0044]
Thereafter, the mixture of powders (A) and (B) is parallel (//) or perpendicular (|) Orienting in a suitable magnetic field and further compressing by a suitable method such as, for example, compression or hydrostatic compression. The obtained compacts are, for example, 3.5 and 4.5 g / cm³Which is sintered between 1050 ° C. and 1110 ° C. and further heat treated in the usual manner.
[0045]
The obtained densities are 7.45 and 7.65 g / cm³And between.
[0046]
The magnet can then undergo any necessary normal mechanical and surface working operations.
[0047]
The magnet according to the invention belongs to the group RE-MT-B, wherein RE represents at least one rare earth element, MT represents at least one transition element such as Fe and / or Co, and B represents boron. And this is mainly a square phase RE called "T1".₂Fe₁₄The second phase mainly includes rare earth elements and may include other small amounts of phases. These magnets have the following characteristics. that is,
Residual value: Br ≧ 1.25T (// at compression)
Residual value: Br ≧ 1.32T (|In compression), even Br ≧ 1.35T. The intrinsic coercive field HcJ ≧ 1150 kA / m (= 14.3 kOe).
[0048]
More specifically, they have a structure consisting of grains of phase T1, constituting more than 94% of the structure, which is substantially uniform in size between 2 and 20 μm. They are surrounded by a narrow, continuous margin of the RE-rich second phase, which is a substantially uniform thickness not ≧ 5 μm. This second phase contains more than 10% cobalt.
[0049]
The present invention will be better understood from the embodiments described below, illustrated by FIGS.
[0050]
【Example】
Example 1
Eight alloys, the compositions of which are shown in Table I, were prepared as shown below.
[0051]
-Vacuum casting of ingots
-Hydrogen treatment under the following conditions,
・ Installation under vacuum
・ Introduction of argon at 0.1 MPa absolute pressure
Heating at 50 ° C / h up to 400 ° C
・ Installation under vacuum
・ 0.06MPa (H₂) And introduction of an argon + hydrogen mixture at an absolute partial pressure of 0.07 MPa (Ar) and holding for 2 hours
・ Installation under vacuum
Introduction of 0.1 MPa of argon and cooling to room temperature at 10 ° C./h
-Milling using a gas jet mill under nitrogen to the Fisher measured particle size shown in Table III.
[0052]
Ten alloys, the compositions of which are shown in Table II, were prepared as shown below.
[0053]
-Vacuum melting of ingots
-Hydrogen treatment under the following conditions,
・ Installation under vacuum
・ 0.06MPa (H₂) And Ar + H at an absolute partial pressure of 0.07 MPa (Ar)₂Introduce mixture and hold for 2 hours
・ Heating up to 400 ° C at 50 ° C / h in the same atmosphere and holding for 2 hours
・ Installation under vacuum
Introduction of argon at an absolute pressure of 0.1 MPa and cooling to room temperature at 10 ° C./h
-Milling using a gas jet mill under nitrogen to the Fisher measured particle size shown in Table III.
[0054]
The powders (A) and (B) produced are mixed in the weight ratios shown in Table V and then mixed with a magnetic field (//|), Compacted and sintered under the conditions specified in Table V, which also shows the density and magnet properties of the magnet.
[0055]
The magnets M1, M2, M3, M4, M5, M9, and M13 are in accordance with the invention, others are outside the scope of the invention for the reasons described below.
[0056]
M6-powder (B) contains 1% B above the limit and is not sufficiently densified.
[0057]
The proportion of the powder (B) contained in the M7-mixture (A) + (B) is too small, the powder (B) is in an insufficiently dispersed state, and the density is not sufficient.
[0058]
Since the alloy (B) having an M8-RE content that is too low is used, the coercive force is lower than 1050 kA / m.
[0059]
The presence of V in the M10—alloy (B) —9% by weight—does not give a good proportion.
[0060]
Simultaneous presence of B and V in M11-powder (B) causes loss of all magnet properties.
[0061]
S1, S2, S3- These compositions have been obtained using a single alloying method, which does not result in sufficient densification, resulting in weak magnet properties.
[0062]
Uses powder (A1) having the same composition as M12-M1 but mixed with powder (B9) that has been treated by mechanical pulverization in an inert gas instead of hydrogen before being introduced into the gas jet mill. It is produced.
[0063]
FIGS. 1 and 2 schematically show two microscope sections taken on a scanning electron microscope equipped with an analytical probe, of the same composition corresponding to the examples M1 and S1 shown below. Performed on two magnets, M1 is produced according to the present invention and S1 is produced using conventional single alloying techniques.
[0064]
The differences are as shown below.
[0065]
The magnet M1 has an average size of 9 μm and a magnet phase RE of fine grains having a size in which 95% of the grains are below 14 μm;₂Fe₁₄B has a uniform structure-1-.
[0066]
-The second phase is rich in RE-2-, the crystal grains RE of the magnet phase₂Fe₁₄It is evenly distributed within a narrow margin around B, where there are no pockets with a size greater than 4 μm.
[0067]
-RE_{1 + e}Fe₄B₄There is no evidence of the presence of porosity, the porosity -3- within the grains is very low, and the pore diameter does not exceed 2μ. There is only a small amount of intragranular oxide phase-4- and the size of these oxides does not exceed 3 μm.
[0068]
-Phase T1 (RE₂Fe₁₄B) and the quantitative analysis of cobalt in the second phase show that cobalt is mainly present in the second grain phase with a content of more than 10% by weight and that the magnet phase RE₂Fe₁₄B-1- is shown to have only a very small cobalt content.
[0069]
The magnet S1 has an average size of 12 μm and a considerable number of grains above 20 μm, some as much as 30 μm;₂Fe₁₄It has the feature of having a microstructure consisting of B-1-. Furthermore, the grains are generally angular. RE Fe₄B₄The presence of the -5-phase should be noted with a number of large voids, which can have a diameter of> 5 μm.
[0070]
Oxide accumulation-4-, which may be-> 5 [mu] m, may be observed mainly at triple contacts.
[0071]
-The Co content of the second phase rich in Re₂Fe₁₄As in B, very low and corresponds to the average content in the alloy.
[0072]
The method of mixing the two powders (A) and (B) according to the invention has the following advantages over the prior art, which are:
The production method for the powder (B) containing mainly Co and RE results in a fine uniform distribution of the constituents for hydrotreating. It ultimately results in better densification, a lower total RE content than in the prior art, further improved magnet properties (Br, HcJ) and improved corrosion resistance. The result is improved.
[0073]
The composition of the powder (B) results in a second phase rich in RE, such as resistance to atmospheric corrosion due to Co or better sintering capacity due to Cu and Al , With special properties.
[0074]
Thus, for example, in a sintered magnet prepared according to the present invention (RE = 30.5% by weight) and in a humid atmosphere (100% relative humidity) under a relative pressure of 1.5 bar (0.15 MPa) The sintered magnet prepared according to the prior art, produced in accordance with the same technique by monoalloying metallurgy and kept in an autoclave at 100 ° C. for 120 h, exhibits the following weight loss: .
[0075]
-Invention 2 to 7.10^-3g / cm²
-Prior art 3 to 7.10^-2g / cm²
If the compositions of the base and the added elements can be compared, the magnets show a markedly different increase in resistance to corrosion, with a factor increase of 10 for the magnets according to the invention.
[0076]
The microstructure of the sintered magnet is more uniform with respect to the grain size of T1, and the coercivity is significantly improved due to the better distribution of the smaller masses of the RE-rich phase. The result is that.
[0077]
At a mixing ratio of powders (A) and (B) within the defined range, the rate of change in boron and RE content substantially corresponds to the optimal RE / B ratio, Phase RE_{1 + e}FE₄B₄It is demonstrated that this method allows for significant adaptability in the powder composition and maximizes the magnetic properties.
[0078]
Example 2
Two alloys (A), whose compositions are shown in Table VI, were prepared as shown below.
[0079]
-Vacuum melting of ingots
-Hydrogen treatment under the following conditions,
・ Installation under vacuum
・ Introduction of argon at 0.1 MPa absolute pressure
Heating at 50 ° C / h up to 400 ° C
・ 0.06MPa (H₂) And introduction of an argon + hydrogen mixture at an absolute partial pressure of 0.07 MPa (Ar) and holding for 2 hours
・ Installation under vacuum
Introduction of argon at an absolute pressure of 0.1 MPa and cooling to room temperature at 10 ° C./h
-Milling using a gas jet mill under nitrogen to the Fisher measured particle size shown in the table.
[0080]
Two alloys (C), whose compositions are shown in Table VII, were prepared as shown below.
[0081]
-Vacuum melting of ingots
-Hydrogen treatment under the following conditions,
・ Installation under vacuum
・ 0.06MPa (H₂) And Ar + H at an absolute partial pressure of 0.07 MPa (Ar)₂Introduce mixture and hold for 2 hours
・ Heating up to 400 ° C at 50 ° C / h in the same atmosphere and holding for 2 hours
・ Installation under vacuum
Introduction of argon at an absolute pressure of 0.1 MPa and cooling to room temperature at 10 ° C./h
The maximum size of the coarse powder produced in this way was below 900 μm.
[0082]
Alloy (D), whose composition is shown in Table VIII, was treated as shown below.
[0083]
Mechanical grinding of the ingot under nitrogen until the measured particle size is <3 mm
Pre-milling in a gas jet mill under nitrogen until the measured particle size is <500 μm
Eight mixtures (B) of (C) + (D), the compositions of which are shown in Table IX, were prepared as shown below.
[0084]
Mixing of the coarse powders (C) and (D) in the weight ratios given in Table IX
-Homogenization in the rotary mixer
-Grinding in a gas jet grinder until the measured particle size specified in Table X
The powders (A) and (B) thus obtained were mixed in the weight ratios shown in Table XI and then (|) Compression and sintering in a magnetic field and subsequent treatment under the conditions given in Table XII, which also lists the magnet properties of the magnet.
[0085]
The magnets M7-M8, M11-M12, M23-M24, M27, M28 correspond to the present invention. The remaining magnets are outside the scope of the claimed invention for the following reasons.
[0086]
M13 to M16 and M29 to M32 contain alloys (B) with too high a B content.
[0087]
M1, M2, M3, M4, M17, M18, M19, and M20 were produced from a mixture in which powder (D) was not added to powder (B). Accordingly, the residual values of the magnet were always lower than for the same composition according to the invention.
[0088]
Examples M5, M6, M9, M10, M13, M14, M21, M22, M25, M26, M29, M30 are produced from powder (B) including powder (D) but have a high boron content (1. (A) having a residual value of less than 1.32T.
[0089]
Examples M31 and M32 were produced from powder (B) containing powder (D) and powder (A) with low boron content (0.98% by weight), but these magnets B) had a B content of> 1.5% and thus had a slightly lower retention value of 1.32T.
[0090]
The magnet according to the invention has the same structural properties as described above, but with Nd_{1 + e}Fe₄B₄Does not exist, shows a uniform grain structure with only a slightly angular size and shape, and the second phase is uniformly dispersed in a narrow margin where only Co is preferentially present.
[0091]
The method of the present invention has the following advantages.
[0092]
Example 1 results in better densification and sintering at lower temperatures and / or for shorter periods of time, as well as improved residual induction and coercivity.
[0093]
The additive powder (B) contains all of the additional elements necessary to form the RE-rich phase during the sintering operation performed at lower temperatures (1050-1070 ° C.) This phase is liquid and contains cobalt, other elements such as aluminum, copper, silicon, and impurities. During cooling after sintering, additional magnet phase RE₂Fe₁₄B is the TR required in the prior art._{1 + e}Fe₄B₄Without the need for complicated dissolution. This results in highly valuable magnet properties.
[0094]
-The sintered magnet of the present invention is TR_{1 + e}Fe₄B₄Contains no phases.
[0095]
The hydrotreatment of the powder (C), as in the prior art, results in a fine and uniform distribution of the constituents, and therefore also for high RE contents, even at low temperatures, during sintering at low temperatures. It facilitates densification, and also facilitates higher magnet property values (Br, Hcj) and improved corrosion resistance.
[0096]
The addition of the boron-containing powder (D) into the powder (C) allows a fine adjustment of the final content of this element in order to maximize the final residual value of the magnet.
[0097]
[Table 1]

[0098]
[Table 2]

[0099]
[Table 3]

[0100]
[Table 4]

[0101]
[Table 5]

[0102]
[Table 6]

[0103]
[Table 7]

[0104]
[Table 8]

[0105]
[Table 9]

[0106]
[Table 10]

[0107]
[Table 11]

[0108]
[Table 12]

[Brief description of the drawings]
FIG. 1 shows schematically a microscopic section of a sintered magnet (M1) according to the invention.
FIG. 2 schematically shows a microscopic section of a sintered magnet (S1) having the same composition obtained using an alloying technique.

Claims (29)

A magnet powder for the manufacture of RE-T-B group sintered magnets, wherein RE represents at least one rare earth element and T represents at least one transition element such as Fe and / or Co. B represents boron, the powder of which may contain small amounts of other elements and has a structure consisting mainly of grains of the square phase RE ₂ T ₁₄ B, the second phase consisting mainly of RE In a magnetic powder consisting of and comprising other minor phases, the initial magnet powder is a mixture of the following two powders (A) and (B):
[A] Powder (A) consists of grains having a square structure RE ₂ T ₁₄ B, where T is predominantly iron with Co / Fe <8%, which further comprises 0.5% And at least one element of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W, and up to 4% in total. May also contain impurities (the composition is indicated by weight) , the Fisher measured particle size is between 3.5 and 5 μm,
b) the powder (B) is rich in RE, contains Co and has the composition given below by weight,
52-70% RE, 130 ×% RE (%) containing at least 40% of one or more light rare earth elements selected from La, Ce, Pr, Nd, Sm, and Eu based on the total weight of the rare earth elements. RE is hydrogen content exceeding representing) the% of RE (wt ppm), which is 20-35% of Co, 0-20% of Fe, 0 -0.2% B, 0.1-4 % of Al And an unavoidable impurity whose powder has a Fisher measured particle size of between 2.5 and 3.5 μm]. 2. The magnet powder according to claim 1, wherein the measured particle size of the powder (B) is at least 20% lower than that of the powder (A) . 3. The magnet powder according to claim 1 or 2, wherein the powder (B) is substantially free of boron. Magnet powder according to any one of claims 1 to 3, characterized in that the liquidus temperature of the powder (B) is below or equal to 1080 ° C. The magnetic powder according to claim 4, wherein the liquidus temperature is lower than 1050C. Magnetic powder according to any one of claims 1 to 5, characterized in that the powder (A) represents 88 to 95% (by weight) of the mixture (A) + (B). Magnetic powder. 7. Magnetic powder according to claim 6, characterized in that the powder (A) represents 90 to 94% (by weight) of the mixture (A) + (B). 5. A process for producing powder (B) according to one of claims 1 to 4, characterized in that the initial alloy is treated with hydrogen under specific conditions before milling, The conditions are set under vacuum, introducing an inert gas at a pressure between 0.1 and 0.12 MPa, and up to a temperature between 350 and 450 ° C., 10 ° C./h and 500 ° C. / H, increasing the temperature at a rate between 1 / h and introducing hydrogen at an absolute partial pressure of between 0.01 and 0.12 MPa, and continuing these conditions for 1 to 4 hours, then applying vacuum And introducing an inert gas at a pressure of 0.1 and 0.12 MPa and cooling to room temperature at a rate between 5 ° C./h and 100 ° C./h. 9. The method of claim 8, wherein the hydrogen treatment comprises maintaining the initial alloy at room temperature at an absolute partial hydrogen pressure between 0.01 and 0.12 MPa for 1 to 3 hours. A method characterized in that it is performed after a processing step. 10. A method according to claim 8 or claim 9, characterized in that the preceding hydrogen treatment step according to claim 9 and the hydrogen treatment according to claim 8 are repeated up to twice. 11. The method according to any one of claims 8 to 10, characterized in that the inert gas is argon or helium or a mixture of the two gases. 2. A process for producing a powder (A) as defined in claim 1, characterized in that, before milling, the initial alloy is treated with hydrogen under the conditions described below, the condition being vacuum. Installed below, with the introduction of an inert gas at a pressure between 0.1 and 0.12 MPa, between 10 ° C./h and 500 ° C./h up to a temperature between 350 and 450 ° C. The temperature is increased at a rate of and hydrogen at an absolute partial pressure of between 0.01 and 0.12 MPa is introduced, and these conditions are maintained for 1 to 4 hours, then placed under vacuum, 1. A process comprising introducing an inert gas at a pressure of 1 and 0.12 MPa and cooling to room temperature at a rate between 5 ° C./h and 100 ° C./h. 13. The method according to claim 12, wherein the inert gas is argon or helium or a mixture of the two gases. Magnet powder produced according to claim 1, characterized in that the RE content is between 29 and 32% by weight. A magnet powder described in claim 14, _{O 2} content has the feature that below 3500 ppm, the magnet powder. 15. The magnet powder according to claim 14, characterized in that the RE content is between 29 and 31% by weight. A RE-T-B group sintered magnet made from the magnet powder of claim 1 , wherein RE represents at least one rare earth element and T is at least one such as Fe and / or Co. Represents one transition element, B represents boron, and the powder may contain other trace elements, and the powder has a structure mainly composed of a crystalline phase of a square phase (T1) RE ₂ T ₁₄ B. Wherein the second phase consists primarily of RE and may comprise other minor phases, with Co being present primarily in the second phase having an average Co content of ≧ 10% by weight A sintered magnet that has the characteristic of 18. The magnet according to claim 17, characterized in that it contains less than 3500 ppm of oxygen. An additive powder (B) according to any one of claims 1 or 2, wherein the additive powder is a mixture of powders (C) and (D):
(A) Powder (C) is rich in RE, contains Co and has a composition indicated by weight below,
52-70% RE, 130 ×% RE (%) containing at least 40% of one or more light rare earth elements selected from La, Ce, Pr, Nd, Sm, and Eu based on the total weight of the rare earth elements. RE stands for% of RE) , hydrogen content (wt ppm), 20-35% Co, 0-20% Fe, 0-0.2% B, 0.1-4% Al , And unavoidable impurities,
b) The powder (D) is composed of B alloyed with at least one of Al, Si, V, Cr, Mn, Fe, Co, Ni, Cu, Nb and Mo, together with unavoidable impurities. Containing between 5 and 70% by weight of B ]. 20. Additive powder (B) according to claim 19, characterized in that the B content is between 0.4 and 1.2%. 20. A magnetic powder comprising a mixture of 88 to 95% of powder (A) and 5 to 12% of powder (B) according to claim 19 , wherein the powder (A) has square grains RE ₂ T. _14B , T consists mainly of iron with Co / Fe ≦ 8% and contains 0.95 to 1.05% B and up to 0.5% Al, 0.05 % Cu and up to a total of 4% of at least one of V, Nb, Hf, Mo, Cr, Ti, Zr, Ta, W, and also unavoidable impurities, Magnetic powder, wherein the Fischer measured particle size is between 3.5 and 5 μm. 21. The additive powder (B) according to claim 19 or 20, wherein the RE-rich powder (C) is substantially free of boron. 23. The additive powder (B) according to claim 22, characterized in that its liquidus temperature is below or equal to 1050C. A magnet powder comprising a mixture of additives powder as described in claim 22 (B), a characteristic that is mixed with the powder (A) having substantially the same composition as that of the magnet phase RE 2 _T 14 _B Magnetic powder . 25. The magnetic powder according to claim 24, characterized in that the measured particle size of the powder (B) is at least 20% lower than that of the powder (A). 18. The sintered magnet according to claim 17, wherein 29 to 32% RE, 0.93 to 1.04% B, 1 to 4.3% Co, 0.2 to 0.5%. A sintered permanent magnet containing 0.02% to 0.05% Cu, the balance being Fe and unavoidable impurities, characterized by a residual value of more than 1.32T. permanent magnet. 28. The permanent magnet according to claim 26, wherein the permanent value is greater than 1.35T. 28. A permanent magnet according to claim 26 or claim 27, characterized in that the intrinsic coercivity is greater than 1150 kA / m. 29. A permanent magnet according to any one of claims 26 to 28, characterized in that the oxygen content is below 3500 ppm.

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